Method and apparatus for determining parameters of linear motion in a surgical instrument

ABSTRACT

A surgical instrument and method of controlling the surgical instrument are disclosed. The surgical instrument includes a housing and an elongated shaft that extends distally from the housing and defines a first longitudinal axis. The surgical instrument also includes a firing rod disposed in the elongated shaft and a drive mechanism disposed at least partially within the housing. The drive mechanism mechanically cooperates with the firing rod to move the firing rod. A sensor senses a parameter of light reflected from the surface of the firing rod, which includes markings that change the reflectivity of the firing rod. The measurement unit determines a parameter of the motion of the firing rod, such as the position and speed of the firing rod, based on the sensed parameter of the light reflected from the surface of the firing rod.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/033,622, filed Feb. 24, 2011, which claims the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 61/314,189,filed on Mar. 16, 2010, the entire contents of which are incorporated byreference herein. U.S. patent application Ser. No. 13/033,622, filedFeb. 24, 2011, is also a Continuation-in-Part of U.S. patent applicationSer. No. 12/189,834, filed on Aug. 12, 2008, which claims the benefitof, and priority to, U.S. Provisional Patent Application Ser. No.60/997,854, filed on Oct. 5, 2007, the entire contents of which areincorporated by reference herein.

BACKGROUND 1. Technical Field

The present disclosure relates to a method and apparatus formanipulating body tissue or deploying surgical fasteners into bodytissue, and, in particular, to a method and apparatus for determiningparameters of the motion of a firing rod in a surgical instrument basedon the change in light reflected from the surface of the firing rod.

2. Background of Related Art

Current surgical instruments typically require 10-60 pounds of manualhand force to clamp body tissue and deploy surgical fasteners in bodytissue. Repeated use of these surgical instruments can cause fatigue ina surgeon's hand. Powered surgical instruments were developed to, amongother reasons, reduce or eliminate this fatigue. These powered surgicalinstruments include gas-powered pneumatic staplers, which implantsurgical fasteners into body tissue. Certain of these instrumentsinclude a pressurized gas supply coupled to a firing mechanism and atrigger mechanism. The trigger mechanism, when depressed, releasespressurized gas, which, in turn, applies force to the firing mechanismto deploy a surgical fastener into body tissue.

Powered surgical instruments also include motor-powered surgicalinstruments. These surgical instruments include powered surgicalstaplers with motors that activate staple firing mechanisms. Typically,the motors are rotary motors mechanically coupled to a lead screw sothat the motor can cause the lead screw to rotate. The lead screw has acontinuous helical thread machined on its outer surface along its length(similar to the thread on a bolt). Threaded onto the lead screw is a nutwith corresponding helical threads. The nut, however, does not rotatewith the lead screw. In this configuration, when the lead screw isrotated by the motor, the nut is driven in a linear direction. The nut,in turn, drives a mechanism for manipulating body tissue or deploying asurgical fastener into body tissue. Alternatively, the lead screw isreplaced by a firing rod with helical threads on its outside surface andthe nut is replaced by a drive tube with corresponding threads on itsinside surface (as described below). In this configuration, the motorrotates the drive tube and the drive tube, in turn, drives the firingrod in a linear direction. The firing rod, in turn, drives the mechanismfor manipulating body tissue or deploying a surgical fastener into bodytissue.

In some surgical instruments, a controller controls the motion of thefiring mechanism (e.g., the nut or the firing rod) based on feedbackfrom sensors that sense parameters of the linear motion of the firingmechanism (e.g., velocity). A conventional method of sensing parametersassociated with the motion of a firing rod is to use a rotational sensormechanically coupled to the rotary motor or the drive tube that drivesthe firing rod.

A typical rotational sensor includes an encoder wheel coupled to thedrive shaft of the rotary motor (or the drive tube), a light generator,and an optical reader (e.g., photo interrupter). The encoder wheelincludes a plurality of slits disposed around its outer edge and rotateswith the drive shaft. The outer edge of the encoder wheel is disposedbetween the light generator and the optical reader so that the lightgenerator emits a light beam through the slits to the optical reader. Inother words, the light beam is interrupted by the encoder wheel as thedrive shaft rotates. The optical reader determines the number ofinterruptions in the light beam and rate of interruptions and transmitsthese measurements to a processor, which determines the speed of thedrive shaft. The processor then uses the speed of the drive shaft tocalculate the linear velocity of the actuator (e.g., firing rod)mechanically coupled to the drive shaft.

Rotational sensors as well as other existing types of sensors, however,contribute in a significant way to the size, length, diameter, weight,and complexity of a surgical instrument. In addition, many of thesesensors increase mechanical wear within the surgical instrument becausethe sensors mechanically interact with or repeatedly make physicalcontact with components of the surgical instrument. Therefore, there isa continual need for surgical instruments having sensors that reducemechanical wear (for increased reliability), that reduce the complexityof the design of the surgical instrument (for reduced fabricationcosts), and that reduce the size, length, diameter, and weight of thesurgical instrument (for increased maneuverability during laparoscopicand endoscopic procedures).

SUMMARY

The present disclosure, in one aspect, features a surgical instrument.The surgical instrument includes a housing, an elongated shaft, a firingrod, a drive mechanism, a motion sensor, and a measurement unit. Theelongated shaft extends distally from the housing and defines a firstlongitudinal axis. The firing rod is disposed within the elongated shaftand the drive mechanism is disposed at least partially within thehousing. The drive mechanism mechanically cooperates with the firingrod. The motion sensor senses a parameter of light (e.g., infraredradiation or light) reflected from the surface of the firing rod. Themeasurement unit determines a parameter of the motion of the firing rodbased on a sensed change in the parameter of the light reflected fromthe surface of the firing rod. This sensor design does not mechanicallyinteract with the firing rod and thus reduces the mechanical wear of thecomponents of the surgical instrument. In addition, this sensor designis simple and minimizes the size of the surgical instrument for optimummaneuverability during surgical procedures.

In some embodiments, the motion sensor includes a light emitter anddetector unit that generates and emits light on the surface of thefiring rod and senses the parameter of the light reflected from thesurface of the firing rod. In some embodiments, the light emitter anddetector unit generates a pulse signal with a parameter that varies withthe change in the parameters of the light reflected from the surface ofthe firing rod. In addition, the measurement unit determines theparameter of the motion of the firing rod based on the change in theparameter of the pulse signal. In some embodiments, the parameter of thepulse signal is the frequency of the pulse signal or the pulse width ofthe pulse signal.

In some embodiments, the measurement unit includes a counter that countspulses in the pulse signal. In these embodiments, the measurement unitalso includes a data processor that computes a pulse signal. In someembodiments, the surface of the firing rod includes a plurality ofmarkings that vary the reflective properties of the surface of thefiring rod. In these embodiments, the measurement unit includes acounter that counts the number of markings that are exposed to the lightemitted from the light emitter and detector unit based on the sensedchange in the parameter of the light reflected from the surface off thefiring rod. In some embodiments, the measurement unit determines theparameter of the motion of the firing rod based on the pulse signalfrequency.

In other embodiments, the parameter of the motion of the firing rod isthe position or velocity of the firing rod and the parameter of thelight is phase, frequency, intensity, or polarization. In yet otherembodiments, the surgical instrument further includes a control unitthat controls the drive mechanism based on the measured parameter of themotion of the firing rod determined by the measurement unit.

The present disclosure, in another aspect, features a method ofdetermining a parameter of the motion of a firing rod in a surgicalinstrument. The method includes emitting light on the surface of afiring rod in a surgical instrument, sensing a change in a parameter ofthe light reflected from the surface of the firing rod, and determininga parameter of the motion of the firing rod based on the sensed changein the parameter of the light reflected from the surface of the firingrod.

The present disclosure, in yet another aspect, features a method ofoperating a surgical instrument. This method includes emitting light onthe surface of a firing rod in a surgical instrument, sensing a changein a parameter of the light reflected from the surface of the firingrod, determining a parameter of the motion of the firing rod based onthe sensed change in the parameter of the light reflected from thesurface of the firing rod, and controlling the motion of the firing rodbased on the determined parameter of the motion of the firing rod.

In some embodiments, sensing a change in a parameter of the lightreflected from the surface of the firing rod includes generating a pulsesignal with a parameter that varies with the change in the parameter ofthe light reflected from the surface of the firing rod, and determiningthe parameter of the motion of the firing rod includes determining theparameter of the motion of the firing rod based on the change in theparameter of the pulse signal. In other embodiments, sensing a change inthe parameter of the light reflected from the surface of the firing rodincludes counting the number of markings on the firing rod that areexposed to the light.

In some embodiments, the parameters of the motion of the firing rodinclude the position or velocity of the firing rod and the parameter ofthe light is phase, frequency, intensity, or polarization.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1 is a perspective view of a surgical instrument including a motionsensor that includes an light emitter and detector unit in accordancewith an embodiment of the present disclosure;

FIG. 2 is a partial perspective view of the powered surgical instrumentof FIG. 1;

FIG. 3 is a top plan view of the powered surgical instrument of FIG. 2;

FIG. 4 is a perspective cut-away view of the powered surgical instrumentof FIG. 2 in accordance with an embodiment of the present disclosure;

FIG. 5 is a perspective view of an articulation mechanism of the poweredsurgical instrument of FIG. 1 in accordance with an embodiment of thepresent disclosure;

FIG. 6 is a partial cross-sectional view of the powered surgicalinstrument of FIG. 1;

FIG. 7 is a partial cross-sectional view of the housing of the poweredsurgical instrument of FIG. 1 in accordance with another embodiment ofthe present disclosure;

FIG. 8 is an exploded perspective view of the mounting assembly and theproximal body portion of a loading unit with parts separated of thepowered surgical instrument of FIG. 1;

FIG. 9 is a side cross-sectional view of an end effector of the poweredsurgical instrument of FIG. 1:

FIG. 10 is a partial side view showing a clutch of the powered surgicalinstrument of FIG. 1;

FIG. 11 is a perspective view of a clutch plate of the clutch of FIG.10;

FIG. 12 is a schematic diagram of a control system in accordance with anembodiment of the present disclosure;

FIG. 13 is a schematic diagram of a feedback control system inaccordance with an embodiment of the present disclosure;

FIGS. 14-15 are perspective front and rear views of a feedbackcontroller of the feedback control system in accordance with anembodiment of the present disclosure;

FIG. 16 is a schematic diagram of the feedback controller in accordancewith an embodiment of the present disclosure;

FIG. 17 is a block diagram of a feedback control system for controllingthe motion of a firing rod in accordance with an embodiment of thepresent disclosure;

FIGS. 18A and 18B are diagrams illustrating how a pulse signal outputfrom a light emitter and detector unit responds to a change in the lightreflected from the surface of the firing rod that results from themotion of the firing rod with respect to the elongated shaft inaccordance with an embodiment of the present disclosure;

FIG. 19 is a flow diagram of a process for determining a parameter ofthe motion of a firing rod in a surgical instrument in accordance withan embodiment of the present disclosure;

FIG. 20 is a flow diagram of a process for operating a surgicalinstrument in accordance with an embodiment of the present disclosure;and

FIGS. 21 and 22 are flow diagrams of processes for determiningparameters of the motion of a firing rod in a surgical instrument inaccordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the presently disclosed surgical instrument are nowdescribed in detail with reference to the drawings, in which likereference numerals designate identical or corresponding elements in eachof the several views. As used herein the term “distal” refers to thatportion of the surgical instrument, or component thereof, farther fromthe user while the term “proximal” refers to that portion of thesurgical instrument or component thereof, closer to the user.

A surgical instrument (e.g., a powered surgical stapler) in accordancewith the present disclosure is referred to in the figures as referencenumeral 10. Referring initially to FIG. 1, powered surgical instrument10 includes a housing 110, an elongated shaft 140 defining a firstlongitudinal axis A-A, and an end effector 160 that defines a secondlongitudinal axis B-B. The elongated shaft 140 extends distally from thehousing 110 and the end effector 160 is disposed adjacent a distalportion of the elongated shaft 140. In some embodiments, the elongatedshaft 140 is configured for minimally invasive surgical procedures.

The housing 110 contains a drive motor 200, a drive tube 210, and afiring rod 220, and a motion sensor 251 (shown by the dotted lines). Thedrive motor 200 may be a rotary motor that drives the drive tube 210 ina radial direction. As described in more detail below, the drive tube210 includes threads on its inner surface that correspond to threads onthe outer surface of the firing rod 220 so that rotation of the drivetube 210 causes the firing rod 220 to move in a linear direction. Thefiring rod 220, in turn, actuates the end effector 160.

In certain surgical procedures, the firing rod 220 and the end effector160 must be precisely controlled. According to embodiments of thepresent disclosure, the motion of the firing rod 220 is preciselycontrolled based on the actual motion of the firing rod 220 that issensed by the motion sensor 251 (which includes an light emitter anddetector unit described below). The motion sensor 251 senses actualmotion of the firing rod 220 by emitting light on the surface of thefiring rod 220 and detecting a parameter of the light reflected from thesurface of the firing rod 220.

According to an embodiment of the present disclosure, end effector 160includes a first jaw member having one or more surgical fasteners (e.g.,cartridge assembly 164) and a second opposing jaw member including ananvil portion for forming the surgical fasteners (e.g., an anvilassembly 162). In some embodiments, staples are housed in cartridgeassembly 164 to apply rows of staples to body tissue either insimultaneous or sequential manner. Either one or both of the anvilassembly 162 and the cartridge assembly 164 are movable in relation toone another between an open position in which the anvil assembly 162 isspaced apart from cartridge assembly 164 and an approximated or clampedposition in which the anvil assembly 162 is in juxtaposed alignment withcartridge assembly 164. In other embodiments, the end effector 160 maybe configured to deploy any type of surgical component used to join bodytissue including fasteners, clips, staples, coils, or sutures. In yetother embodiments, the end effector 160 may be configured to rotate,articulate, extend, retract, clamp or cut.

End effector 160 is pivotably attached to a mounting portion 166, which,in turn, is attached to a body portion 168. Body portion 168 may beintegral with the elongated shaft 140 of the surgical instrument 10, ormay be removably attached to the surgical instrument 10 to provide areplaceable, disposable loading unit (DLU) or single use loading unit(SULU) (e.g., loading unit 169). In certain embodiments, the reusableportion may be configured for sterilization and re-use in a subsequentsurgical procedure.

The loading unit 169 may connect to the elongated shaft 140 through abayonet connection. The loading unit 169 may include an articulationlink that connects the end effector 160 to the firing rod 220 so thatthe end effector 160 is articulated as the firing rod 220 is translatedin the distal-proximal direction along the first longitudinal axis A-A.Other components for connecting end effector 160 to the elongated shaft140 to allow articulation may be used, such as a flexible tube or a tubeincluding a plurality of pivotable members.

The loading unit 169 may incorporate or be configured to incorporatevarious end effectors, such as vessel sealing devices, linear staplingdevices, circular stapling devices, cutters, etc. These end effectorsmay be coupled to the elongated shaft 140 of the powered surgicalinstrument 10. The loading unit 169 may include a linear stapling endeffector that does not articulate. An intermediate flexible shaft may beincluded between a handle portion 112 and the loading unit 169. Aflexible shaft may facilitate access to and/or within certain areas ofthe body.

As shown in FIGS. 1 and 2, the housing 110 includes the handle portion112 on which a main drive switch 114 is disposed. The switch 114 mayinclude first and second switches 114 a, 114 b, which together form atoggle switch. The handle portion 112, which defines a handle axis H-H,is configured to be grasped by fingers of a user. The handle portion 112has an ergonomic shape providing ample palm grip leverage, which helpskeep the handle portion 112 from being squeezed out of the user's handduring operation. Each switch 114 a, 114 b is shown as being disposed ata suitable location on the handle portion 112 to facilitate itsdepression by a user's finger or fingers. In another embodiment, thesurgical instrument 10 includes two separates switches 114 a, 114 bseparated by a rib feature.

Additionally, switches 114 a, 114 b may be used for starting and/orstopping movement of a drive motor 200 (FIGS. 1, 4 and 6). In oneembodiment, the switch 114 a is configured to activate the drive motor200 in a first direction to advance firing rod 220 (FIGS. 1 and 6) in adistal direction thereby clamping the anvil and cartridge assemblies162, 164. Conversely, the switch 114 b may be configured to retract thefiring rod 220 to open the anvil and cartridge assemblies 162, 164 byactivating the drive motor 200 in a second direction opposite of thefirst direction. The retraction mode initiates a mechanical lock out,inhibiting further progression of stapling and cutting by the loadingunit 169. The toggle has a first position for activating switch 114 a, asecond position for activating switch 114 b, and a neutral positionbetween the first and second positions.

The housing 110, in particular the handle portion 112, includes switchshields 117 a, 117 b. The switch shields 117 a, 117 b may have arib-like shape surrounding the bottom portion of the switch 114 a andthe top portion of the switch 114 b, respectively. The switch shields117 a, 117 b minimize accidental activation of the switches 114 a, 114b. Further, the switches 114 a, 114 b have high tactile feedbackrequiring increased pressure for activation.

In one embodiment, the switches 114 a, 114 b are configured asmulti-speed (e.g., two or more speeds), incremental-speed orvariable-speed switches that control the speed of the drive motor 200and the firing rod 220 in a non-linear manner. For example, the switches114 a, 114 b can be pressure-sensitive. This type of control interfaceallows for the gradual increase in the rate of the speed of the drivecomponents from a slower and more precise mode to a faster operation. Tominimize accidental activation of retraction, the switch 114 b may bedisconnected electronically until a fail-safe switch is pressed. Inaddition, a third switch 114 c may also be used for this purpose.Additionally or alternatively, the fail safe can be overcome by pressingand holding the switch 114 b for a predetermined period of time fromabout 100 ms to about 2 seconds. The firing rod 220 then automaticallyretracts to its initial position unless the switch 114 c is activated(e.g., pressed and released) during the retraction mode to stop theretraction. Subsequent pressing of the switch 114 b resumes theretraction of the firing rod 220. Alternatively, in other embodiments,the retraction of the firing rod 220 can continue to full retractioneven if the switch 114 b is released. Other embodiments include anauto-retract mode of the firing rod 220 that fully retracts the firingrod 220 even if switch 114 b is released. The retraction mode may beinterrupted at any time if one of the switches 114 a, 114 b is actuated.

The switches 114 a, 114 b are coupled to a non-linear speed controlcircuit 115 which can be implemented as a voltage regulation circuit, avariable resistance circuit, or a microelectronic pulse width modulationcircuit. The switches 114 a, 114 b may interface with the controlcircuit 115 (FIG. 4) by displacing or actuating variable controldevices, such as rheostatic devices, multiple position switch circuit,linear and/or rotary variable displacement transducers, linear and/orrotary potentiometers, optical encoders, ferromagnetic sensors, and HallEffect sensors. This allows the switches 114 a, 114 b to operate thedrive motor 200 in multiple speed modes, such as gradually increasingthe speed of the drive motor 200 either incrementally or graduallydepending on the type of the control circuit 115 being used, based onthe depression of the switches 114 a, 114 b.

In a particular embodiment, the switch 114 c may be actuated tomechanically and/or electrically change the mode of operation fromclamping to firing. The switch 114 c is recessed within the housing 110and has high tactile feedback to inhibit false actuations. Providing aseparate control switch to initialize the firing mode allows for thejaws of the end effector to be repeatedly opened and closed so that thesurgical instrument 10 is used as a grasper until the switch 114 c ispressed to activate the stapling and/or cutting. The switch 114 mayinclude one or more microelectronic membrane switches. Such amicroelectronic membrane switch includes a relatively low actuationforce, a small package size, an ergonomic size and shape, a low profile,an ability to include molded letters on the switch, symbols, depictionsand/or indications, and a low material cost. Additionally, the switches114 a, 114 b (such as microelectronic membrane switches) may be sealedto help facilitate sterilization of the surgical instrument 10, as wellas to help inhibit particle and/or fluid contamination.

As an alternative to, or in addition to the switches 114 a, 114 b, otherinput devices may include voice input technology, which may includehardware and/or software incorporated in a control system (not shown),or a separate digital module. The voice input technology may includevoice recognition, voice activation, voice rectification and/or embeddedspeech. The user may control the operation of the instrument in whole orin part through voice commands, thus freeing one or both of the user'shands for operating other instruments. Voice or other audible output mayalso be used to provide the user with feedback.

Referring to FIG. 3, a proximal area 118 of the housing 110 includes auser interface 120. The user interface 120 includes a screen 122 and aplurality of switches 124. The user interface 120 may display varioustypes of operational parameters of the surgical instrument 10 such as“mode” (e.g., rotation, articulation or actuation). Operationalparameters may be communicated to the user interface 120 via a sensor.Operational parameters may include “status” (e.g., speed of rotation,angle of articulation or type of actuation) and “feedback,” such aswhether staples have been fired based on the information reported by thesensors disposed in the surgical instrument 10. Error codes and othercodes (e.g., improper loading, replace battery, battery level, andestimated number of firings remaining) may also be communicated to theuser interface 120.

The screen 122 may be an LCD screen, a plasma screen, electroluminescentscreen and the like. In one embodiment the screen 122 may be a touchscreen, obviating the need for the switches 124. The touch screen mayincorporate resistive, surface wave, capacitive, infrared, strain gauge,optical, dispersive signal or acoustic pulse recognition touch screentechnologies. The touch screen may allow the user to provide input whileviewing operational feedback. This approach may enable facilitation ofsealing screen components to help sterilize the surgical instrument 10,as well as inhibiting particle and/or fluid contamination. In certainembodiments, the screen 122 is pivotably or rotatably mounted to thesurgical instrument 10 for flexibility in viewing the screen 122 duringuse or preparation (e.g., via a hinge or ball-and-socket mount).

The switches 124 may be used for starting and/or stopping movement ofthe surgical instrument 10 as well as selecting the pivot direction,speed and/or torque. Also, at least one switch 124 may be used forselecting an emergency mode that overrides various settings. Theswitches 124 may also be used for selecting various options on thescreen 122, such as responding to prompts while navigating userinterface menus and selecting various settings, allowing a user to inputdifferent body tissue types and various sizes and lengths of staplecartridges.

The switches 124 may be formed from a micro-electronic tactile ornon-tactile membrane, a polyester membrane, elastomer, plastic or metalkeys of various shapes and sizes. Additionally, switches may bepositioned at different heights from one another and/or may includeraised indicia or other textural features (e.g., concavity or convexity)to allow a user to depress an appropriate switch without the need tolook at user interface 120.

In addition to the screen 122, the user interface 120 may include one ormore visual outputs 123 which may include one or more colored visiblelights or light emitting diodes (“LEDs”) to provide feedback to theuser. The visual outputs 123 may include corresponding indicators ofvarious shapes, sizes and colors having numbers and/or text whichidentify the visual outputs 123. The visual outputs 123 are disposed ontop of the housing 110 such that the outputs 123 are raised and protrudein relation to the housing 110, providing for better visibility of thevisual outputs 123.

The visual outputs 123 may be displayed in a certain combination toindicate a specific operational mode to the user. In one embodiment, thevisual outputs 123 include a first light (e.g., yellow) 123 a, a secondlight (e.g., green) 123 b and a third light (e.g., red) 123 c. Thelights are operated in a particular combination associated with aparticular operational mode. For example, the first light turned on andthe second and third lights turned off may indicate that the loadingunit 169 and staple cartridge are loaded and power is activated,allowing the end effector 160 to clamp as a grasper and articulate. Inanother embodiment, the visual output 123 may include a singlemulti-colored LED which displays a particular color associated with aparticular operational mode.

The user interface 120 also includes audio outputs 125 (e.g., tones,bells, buzzers, and integrated speaker) to communicate various statuschanges to the user (e.g., low battery and empty cartridge). Audiblefeedback can be used in conjunction with or in lieu of the visualoutputs 123. The audible feedback may be provided in the forms ofclicks, snaps, beeps, rings, and buzzers in single or multiple pulsesequences. In one embodiment, a simulated mechanical sound may beprerecorded that replicates the click and/or snap sounds generated bymechanical lockouts and mechanisms of conventional non-poweredinstruments. This eliminates the need to generate these mechanicalsounds through the actual components of the surgical instrument 10 andalso avoids the use of beeps and other electronic sounds which areusually associated with other operating room equipment, therebyminimizing or eliminating confusion from extraneous audible feedback.

The surgical instrument 10 may also provide for haptic or vibratoryfeedback through a haptic mechanism (not explicitly shown) within thehousing 110. The haptic feedback may be used in conjunction with theauditory and visual feedback or in lieu of it to avoid confusion withthe operating room equipment which relies on audio and visual feedback.The haptic mechanism may be an asynchronous motor that vibrates in apulsating manner. In one embodiment, the vibrations are at a frequencyof about 30 Hz or above, providing a displacement having an amplitude of1.5 mm or lower to limit the vibratory effects from reaching the loadingunit 169.

The user interface 120 may also include different colors and/orintensities of text on the screen 122 and/or on the switches 124 forfurther differentiation between the displayed items. The visual,auditory or haptic feedback can be increased or decreased in intensity.For example, the intensity of the feedback may be used to indicate thatthe forces on the instrument are becoming excessive.

FIGS. 1-5 illustrate an articulation mechanism 170, including anarticulation housing 172, a powered articulation switch 174, anarticulation motor 132 and a manual articulation knob 176. Thearticulation switch 174 may be a rocker and/or a slide switch having anarm 174 a and 174 b on each side of the housing 110 allowing for eitherright or left hand usage of the articulation switch 174. Translation ofthe powered articulation switch 174 or pivoting of the manualarticulation knob 176 activates the articulation motor 132, which thenactuates an articulation gear 233 of the articulation mechanism 170 asshown in FIG. 5. Actuation of articulation mechanism 170 causes the endeffector 160 to move from its first position, where longitudinal axisB-B is substantially aligned with longitudinal axis A-A, towards aposition in which longitudinal axis B-B is disposed at an angle tolongitudinal axis A-A. Preferably, a plurality of articulated positionsis achieved. The powered articulation switch 174 may also incorporatesimilar non-linear speed controls as the clamping mechanism ascontrolled by the switches 114 a, 114 b.

Further, the housing 110 includes switch shields 167 having a wing-likeshape and extending from the top surface of the housing 110 over theswitch 174. The switch shields 167 minimize accidental activation of theswitch 174 when the surgical instrument 10 is placed down or fromphysical obstructions during use and require the user to reach below theshields 167 in order to activate the articulation mechanism 170.

Additionally, articulation housing 172 and powered articulation switch174 are mounted to a rotating housing assembly 180. Rotation of arotation knob 182 about first longitudinal axis A-A causes housingassembly 180 as well as articulation housing 172 and poweredarticulation switch 174 to rotate about first longitudinal axis A-A, andthus causes corresponding rotation of distal portion 224 of firing rod220 (FIG. 6) and end effector 160 about first longitudinal axis A-A. Thearticulation mechanism 170 is electro-mechanically coupled to first andsecond conductive rings 157 and 159 which are disposed on the housingnose assembly 155 as shown in FIG. 4. The conductive rings 157 and 159may be soldered and/or crimped onto the nose assembly 155 and are inelectrical contact with the power source 400 thereby providingelectrical power to the articulation mechanism 170. The nose assembly155 may be modular (e.g., separate from the housing 110) and may beattached to the housing 110 during assembly to allow for easiersoldering and/or crimping of the rings. The articulation mechanism 170includes one or more brush and/or spring loaded contacts in contact withthe conductive rings 157 and 159 such that, as the housing assembly 180(FIG. 3) is rotated along with the articulation housing 172, thearticulation mechanism 170 is in continuous contact with the conductiverings 157 and 159 thereby receiving electrical power from the powersource 400.

Further details of articulation housing 172, powered articulation switch174, manual articulation knob 176 and providing articulation to endeffector 160 are described in detail in commonly-owned U.S. patentapplication Ser. No. 11/724,733 filed Mar. 15, 2007, the contents ofwhich are hereby incorporated by reference in their entirety.

As illustrated in FIGS. 4 and 6, embodiments of the surgical instrument10 include a motion sensor 251 that is electrically coupled (252) to thefiring rod 220. The motion sensor 251 may sense the position of thefiring rod 220 relative to the elongated shaft 140. The motion sensor251 may be used alone or in combination with other sensors includinglimit switches, proximity sensors (e.g., optical and/or ferromagnetic),linear variable displacement transducers, and shaft encoders, which maybe disposed within housing 110, to control and/or measure anarticulation angle of end effector 160 and/or a position of the firingrod 220.

FIGS. 4-8 illustrate various internal components of the surgicalinstrument 10, including a drive motor 200, a drive tube 210, and afiring rod 220 having a proximal portion 222 and a distal portion 224.The drive tube 210 is rotatable about drive tube axis C-C. Drive motor200 is disposed in mechanical cooperation with drive tube 210 and isconfigured to rotate the drive tube 210 about drive gear axis C-C. Inone embodiment, the drive motor 200 may be an electrical motor or a gearmotor, which may include gearing incorporated within its housing. Firingrod coupling 190 provides a link between the proximal portion 222 andthe distal portion 224 of the firing rod 220. Specifically, the firingrod coupling 190 enables rotation of the distal portion 224 of thefiring rod 220 with respect to proximal portion 222 of firing rod 220.Thus, firing rod coupling 190 enables the proximal portion 222 of thefiring rod 220 to remain non-rotatable, as discussed below withreference to an alignment plate 350, while allowing rotation of distalportion 224 of firing rod 220 (e.g., upon rotation of rotation knob182).

With reference to FIGS. 6 and 7, the proximal portion 222 of firing rod220 includes a threaded portion 226, which extends through aninternally-threaded portion 212 of drive tube 210. This relationshipbetween firing rod 220 and drive tube 210 causes firing rod 220 to movedistally and/or proximally, in the directions of arrows D and E, alongthreaded portion 212 of drive tube 210 upon rotation of drive tube 210in response to the rotation of the drive motor 200. As the drive tube210 rotates in a first direction (e.g., clockwise), firing rod 220 movesproximally (i.e., in the direction of arrow E). As illustrated in FIG.6, the firing rod 220 is disposed at its proximal-most position. As thedrive tube 210 rotates in a second direction (e.g., counter-clockwise),firing rod 220 moves distally (i.e., in the direction of arrow D). Asillustrated in FIG. 7, the firing rod 220 is disposed at its distal-mostposition.

The firing rod 220 is distally and proximally translatable withinparticular limits. Specifically, a first end 222 a of proximal portion222 of firing rod 220 acts as a mechanical stop in combination with analignment plate 350. That is, upon retraction, when firing rod 220 istranslated proximally, first end 222 a contacts a distal surface 351 ofalignment plate 350, thus inhibiting continued proximal translation offiring rod 220 as shown in FIG. 6. Additionally, the threaded portion226 of the proximal portion 222 acts as a mechanical stop in combinationwith the alignment plate 350. That is, when firing rod 220 is translateddistally, the threaded portion 226 contacts a proximal surface 353 ofthe alignment plate 350, thus inhibiting further distal translation ofthe firing rod 220 as shown FIG. 7.

The alignment plate 350 includes an aperture, which has a non-roundcross-section. The non-round cross-section of the aperture inhibitsrotation of the proximal portion 222 of the firing rod 220, thuslimiting the proximal portion 222 of the firing rod 220 to axialtranslation through the aperture. Further, a proximal bearing 354 and adistal bearing 356 are disposed at least partially around drive tube 210to facilitate the rotation of the drive tube 210, while helping aligndrive tube 210 within housing 110. The drive tube 210 includes a distalradial flange 210 a and a proximal radial flange 210 b on each end ofthe drive tube 210 which retain the drive tube 210 between the distalbearing 356 and the proximal bearing 354, respectively.

Rotation of drive tube 210 in a first direction (e.g.,counter-clockwise) corresponds to distal translation of the firing rod220, which actuates jaw members 162, 164 of the end effector 160 tograsp or clamp tissue. Additional distal translation of firing rod 220ejects surgical fasteners from the end effector 160 to fasten tissue byactuating cam bars and/or an actuation sled 74 (FIG. 9). Further, thefiring rod 220 may also be configured to actuate a knife (not explicitlyshown) to sever tissue. Proximal translation of firing rod 220corresponding with rotation of the drive tube 210 in a second direction(e.g., clockwise) actuates the anvil and cartridge assemblies 162, 164(FIG. 9) and/or knife to retract or return to corresponding pre-firedpositions. Further details of firing and otherwise actuating endeffector 160 are described in detail in commonly-owned U.S. Pat. No.6,953,139 to Milliman et al. (the ^(c)139 patent), the entire disclosureof which is hereby incorporated by reference.

FIG. 8 shows an exploded view of the loading unit 169. The end effector160 may be actuated by an axial drive assembly 213 having a drive beamor drive member 266. The distal end of the drive beam 213 may include aknife blade. In addition, the drive beam 213 includes a retention flange40 having a pair of cam members 40 a, which engage the anvil andcartridge assemblies 162, 164 during advancement of the drive beam 213longitudinally. The drive beam 213 advances an actuation sled 74longitudinally through the staple cartridge 164. As shown in FIG. 9, thesled 74 has cam wedges for engaging pushers 68 disposed in slots of thecartridge assembly 164, as the sled 74 is advanced. Staples 66 disposedin the slots are driven through tissue and against the anvil assembly162 by the pushers 66.

With reference to FIG. 10, a drive motor shaft 202 is shown extendingfrom a planetary gear 204 that is attached to the drive motor 200. Thedrive motor shaft 202 mechanically cooperates with the clutch 300. Thedrive motor shaft 202 is rotated by the drive motor 200, thus resultingin rotation of clutch 300. The clutch 300 includes a clutch plate 700and a spring 304 and is shown having wedged portions 702 disposed on theclutch plate 700, which are configured to mate with an interface (e.g.,wedges 214) disposed on a proximal face 216 of the drive tube 210.

Spring 304 is illustrated between planetary gear 204 and the drive tube210. Specifically, and in accordance with the embodiment illustrated inFIG. 10, spring 304 is illustrated between the clutch plate 700 and aclutch washer 308. Additionally, drive motor 200 and planetary gear 204are mounted on a motor mount 310. As illustrated in FIG. 10, motor mount310 is adjustable proximally and distally with respect to housing 110via slots 312 disposed in motor mount 310 and protrusions 314 disposedon the housing 110.

In an embodiment of the disclosure, the clutch 300 is implemented as aslip unidirectional clutch to limit torque and high inertial loads onthe drive components. Wedged portions 702 of the clutch 300 areconfigured and arranged to slip with respect to the wedges 214 of theproximal face 216 of the drive tube 210 unless a threshold force isapplied to the clutch plate 700 via the clutch spring 304. Further, whenspring 304 applies the threshold force needed for the wedged portions702 and wedges 214 to engage without slipping, the drive tube 210 willrotate upon rotation of drive motor 200. The wedged portions 702 and/orwedges 214 may be configured to slip in one and/or both directions(i.e., clockwise and/or counter-clockwise) with respect to one anotherwhen a firing force is attained on the firing rod 220.

As illustrated in FIGS. 10 and 11, the clutch 300 is shown with aunidirectional clutch plate 700. The clutch plate 700 includes aplurality of wedged portions 702 having a slip face 704 and a grip face706. The slip face 704 has a curved edge which engages the wedges 214 ofthe drive tube 210 up to a predetermined load. The grip face 706 has aflat edge which fully engages the drive tube 210 and inhibits slippage.

When the clutch plate 700 is rotated in a first direction (e.g.,clockwise), the grip face 706 of the wedged portions 702 engage thewedges 214 without slipping, providing for full torque from the drivemotor 200. When the clutch plate 700 is rotated in a reverse direction(e.g., counterclockwise) the slip face 704 of the wedged portions 702engage the wedges 214 and limit the torque being transferred to thedrive tube 210. Thus, if the load being applied to the slip face 704 isover the limit, the clutch 300 slips and the drive tube 210 is notrotated. This inhibits high load damage to the end effector 160 ortissue which can occur due to the momentum and dynamic friction of thedrive components. More specifically, the drive mechanism of the surgicalinstrument 10 can drive the firing rod 220 in a forward direction withless torque than in reverse. Use of a unidirectional clutch eliminatesthis problem. In addition electronic clutch may also be used to increasethe motor potential during retraction (e.g., driving the firing rod 220in reverse along with the drive motor 200, drive tube 210, clutchassembly 300, alignment plate 350, and any portion of the firing rod220) as discussed in more detail below.

Drive motor shaft 202 may include a D-shaped cross-section 708, whichincludes a substantially flat portion 710 and a rounded portion 712.Thus, while drive motor shaft 202 is translatable with respect to clutchplate 700, drive motor shaft 202 will not “slip” with respect to clutchplate 700 upon rotation of drive motor shaft 202. That is, rotation ofdrive motor shaft 202 will result in a slip-less rotation of clutchplate 700.

The loading unit, in certain embodiments according to the presentdisclosure, includes an axial drive assembly that cooperates with firingrod 220 to approximate anvil assembly 162 and cartridge assembly 164 ofend effector 160, and fire staples from the staple cartridge. The axialdrive assembly may include a beam that travels distally through thestaple cartridge and may be retracted after the staples have been fired,as discussed above and as disclosed in certain embodiments of the '139Milliman patent.

With reference to FIG. 4, the surgical instrument 10 includes a powersource 400 which may be a rechargeable battery (e.g., lead-based,nickel-based, or lithium-ion based). The power source 400 may include atleast one disposable battery. The disposable battery may be betweenabout 9 volts and about 30 volts.

The power source 400 includes one or more battery cells 401 depending onthe current load needs of the surgical instrument 10. Further, the powersource 400 includes one or more ultracapacitors 402 which act assupplemental power storage due to their much higher energy density thanconventional capacitors. Ultracapacitors 402 can be used in conjunctionwith the cells 401 during high energy draw. The ultracapacitors 402 canbe used for a burst of power when energy is desired/required morequickly than can be provided solely by the cells 401 (e.g., whenclamping thick tissue, rapid firing, clamping, etc.), as cells 401 aretypically slow-drain devices from which current cannot be quickly drawn.This configuration can reduce the current load on the cells therebyreducing the number of the cells 401 and/or extending the life of thecells 401. The cells 401 may be connected to the ultracapacitors 402 tocharge the capacitors.

The power source 400 may be removable along with the drive motor 200 toprovide for recycling of these components and reuse of the surgicalinstrument 10. In another embodiment, the power source 400 may be anexternal battery pack, which is worn on a belt and/or harness by theuser and wired to the surgical instrument 10 during use.

The power source 400 is enclosed within an insulating shield 404 whichmay be formed from an absorbent, flame resistant and retardant material.The shield 404 electrically and thermally isolates components of thesurgical instrument 10 from the power source 400. More specifically, theshield 400 inhibits heat generated by the power source 400 from heatingother components of the surgical instrument 10. In addition, the shield404 may also be configured to absorb any chemicals or fluids which mayleak from the cells 402 during heavy use and/or damage.

The power source 400 is coupled to a power adapter 406 which isconfigured to connect to an external power source (e.g., DCtransformer). The external power source may be used to recharge thepower source 400 or provide for additional power requirements. The poweradapter 406 may also be configured to interface with electrosurgicalgenerators which can then supply power to the surgical instrument 10. Inthis configuration, the surgical instrument 10 also includes an AC-to-DCpower source which converts RF energy from the electrosurgicalgenerators and powers the surgical instrument 10. In another embodimentthe power source 400 is recharged using an inductive charging interface.The power source 400 is coupled to an inductive coil (not explicitlyshown) disposed within the proximal portion of the housing 110. Uponbeing placed within an electromagnetic field, the inductive coilconverts the energy into electrical current that is then used to chargethe power source 400. The electromagnetic field may be produced by abase station (not explicitly shown) that is configured to interface withthe proximal portion of the housing 110, such that the inductive coil isenveloped by the electromagnetic field. This configuration eliminatesthe need for external contacts and allows for the proximal portion ofthe housing 110 to seal the power source 400 and the inductive coilwithin a water-proof environment which inhibits exposure to fluids andcontamination.

With reference to FIG. 6, the surgical instrument 10 also includes oneor more safety circuits such as a discharge circuit 410 and a motor andbattery operating module 412. For clarity, wires and other circuitelements interconnecting various electronic components of the surgicalinstrument 10 are not shown, but such wires and other circuit elementsare contemplated by the present disclosure. Certain components of thesurgical instrument 10 communicate wirelessly.

The discharge circuit 410 is coupled to a switch 414 and a resistiveload 417 which, in turn, are coupled to the power source 400. The switch414 may be a user-activated or an automatic (e.g., timer, counter)switch which is activated when the power source 400 needs to be fullydischarged for a safe and low temperature disposal (e.g., at the end ofsurgical procedure). Once the switch 414 is activated, the load 417 iselectrically connected to the power source 400 such that the potentialof the power source 400 is directed to the load 417. The automaticswitch may be a timer or a counter which is automatically activatedafter a predetermined operational time period or number of uses todischarge the power source 400. The load 417 has a predeterminedresistance sufficient to fully and safely discharge all of the cells401.

The motor and battery operating module 412 is coupled to one or morethermal sensors 413 which determine the temperature within the drivemotor 200 and the power source 400 to ensure safe operation of thesurgical instrument 10. The sensors may be an ammeter for determiningthe current draw within the power source 400, a thermistor, athermopile, a thermocouple, a thermal infrared sensor and the like.Monitoring temperature of these components allows for a determination ofthe load being placed on these components. The increase in the currentflowing through these components causes an increase in the temperatureof these components. The temperature and/or current draw data may thenbe used to control the power consumption in an efficient manner orassure safe levels of operation.

To ensure safe and reliable operation of the surgical instrument 10, itis desirable to ensure that the power source 400 is authentic and/orvalid (e.g., conforms to strict quality and safety standards) and isoperating within a predetermined temperature range. Authentication thatthe power source 400 is valid minimizes risk of injury to the patientand/or the user due to poor quality.

Referring again to FIGS. 4 and 6, some embodiments of the surgicalinstrument may include, in addition to the motion sensor 251, aplurality of sensors for providing feedback information relating to thefunction of the surgical instrument 10. Any combination of sensors maybe disposed within the surgical instrument 10 to determine its operatingstage, such as, staple cartridge load detection as well as its status,articulation, clamping, rotation, stapling, cutting and retracting, andthe like. The sensors can be actuated by proximity, displacement orcontact of various internal components of the surgical instrument 10(e.g., firing rod 220 and drive motor 200).

In the illustrated embodiments, the sensors can be rheostats (e.g.,variable resistance devices), current monitors, conductive sensors,capacitive sensors, inductive sensors, thermal-based sensors, limitactuated switches, multiple position switch circuits, pressuretransducers, linear and/or rotary variable displacement transducers,linear and/or rotary potentiometers, optical encoders, ferromagneticsensors, Hall Effect sensors, and proximity switches. The sensorsmeasure rotation, velocity, acceleration, deceleration, linear and/orangular displacement, detection of mechanical limits (e.g., stops), etc.This is attained by implementing multiple indicators arranged in eitherlinear or rotational arrays on the mechanical drive components of thesurgical instrument 10. The sensors then transmit the measurements tothe microcontroller 500 which determines the operating status of thesurgical instrument 10. In addition, the microcontroller 500 alsoadjusts the motor speed or torque of the surgical instrument 10 based onthe measured feedback.

In embodiments where the clutch 300 is implemented as a slip clutch asshown in FIGS. 11 and 12, linear displacement sensors (e.g., motionsensor 251 in FIGS. 4 and 6) are positioned distally of the clutch 300to provide accurate measurements. In this configuration, slippage of theclutch 300 does not affect the position, velocity and accelerationmeasurements recorded by the sensors.

With reference to FIG. 4, a load switch 230 is disposed within thearticulation housing 172. The switch 230 is connected in series with theswitch 114, inhibiting activation of the surgical instrument 10 unlessthe loading unit 169 (FIG. 1) is properly loaded into the surgicalinstrument 10. If the loading unit 169 is not loaded into the surgicalinstrument 10, the main power switch (e.g., switch 114) is open, therebyinhibiting use of any electronic or electric components of the surgicalinstrument 10. This also inhibits any possible current draw from thepower source 400 allowing the power source 400 to maintain a maximumpotential over its specified shelf life.

Thus, the switch 230 acts as a so-called “lock-out” switch whichinhibits false activation of the surgical instrument 10 since the switchis inaccessible to external manipulation and can only be activated bythe insertion of the loading unit 169. The switch 230 is activated bydisplacement of a plunger or sensor tube as the loading unit 169 isinserted into the elongated shaft 140. Once the switch 230 is activated,the power from the power source 400 is supplied to the electroniccomponents (e.g., sensors, microcontroller 500, etc.) of the surgicalinstrument 10 providing the user with access to the user interface 120and other inputs/outputs. This also activates the visual outputs 123 tolight up according to the light combination indicative of a properlyloaded loading unit 169 wherein all the lights are off as described inTable 1.

Once the loading unit 169 is inserted into the elongated shaft, theswitch 230 also determines whether the loading unit 169 is loadedcorrectly based on the position thereof. If the loading unit 169 isimproperly loaded, the switch 114 is not activated and an error code isrelayed to the user via the user interface 120 (e.g., all the lights areoff as described in Table 1). If the loading unit 169 has already beenfired, any mechanical lockouts have been previously activated or thestaple cartridge has been used, the surgical instrument 10 relays theerror via the user interface 120, e.g., the first light 123 a isflashing.

In one embodiment, a second lock-out switch 259 (FIG. 4) coupled to themain switch 114 may be implemented in the surgical instrument 10 as abioimpedance, capacitance or pressure sensor disposed on the top surfaceof the handle portion 112 configured to be activated when the usergrasps the surgical instrument 10. Thus, unless the surgical instrument10 is grasped properly, the operation of the switch 114 is disabled.

Referring to FIG. 6, the surgical instrument 10 includes a positioncalculator 416 for determining and outputting the current linearposition of the firing rod 220. The position calculator 416 iselectrically coupled to the motion sensor 251, which, in someembodiments, senses the markings on the firing rod 220 using an lightemitter and detector unit. The position calculator 416 calculates thecurrent linear position of the firing rod 220 based on a sensor signaloutput from the motion sensor 251.

In some embodiments, the position calculator 416 may be electricallycoupled to other supplemental sensors including a linear displacementsensor 237 and a rotation speed detecting apparatus 418 that is coupledto the drive motor 200. The rotation speed apparatus 418 includes anencoder 420 coupled to the motor for producing two or more encoder pulsesignals in response to the rotation of the drive motor 200. The encoder420 transmits the pulse signals to the apparatus 418, which thendetermines the rotational speed of the drive motor 200. The positioncalculator 416 thereafter determines the linear speed and position ofthe firing rod based on the rotational speed of the drive motor 200since the rotation speed is directly proportional to the linear speed ofthe firing rod 220. The position calculator 416 and the speed calculator422 are in communication with the microcontroller 500, which controlsthe drive motor 200 in response to the sensed feedback from the positionand speed calculators 416, 422.

The surgical instrument 10 may include first and second indicators 320a, 320 b disposed on the firing rod 220, which determine the speed offiring rod 220 and the location of firing rod 220 with respect to drivetube 210 and/or housing 110. For instance, a limit switch may beactivated (e.g., shaft start position sensor 231 and clamp positionsensor 232) by sensing first and second indicators 320 a and/or 320 b(e.g., bumps, grooves, indentations, etc.) passing thereby to determineposition of firing rod 220, speed of firing rod 220 and mode of thesurgical instrument 10 (e.g., clamping, grasping, firing, sealing,cutting, retracting). Further, the feedback received from first andsecond indicators 320 a, 320 b may be used to determine when firing rod220 should stop its axial movement (e.g., when drive motor 200 shouldcease) depending on the size of the particular loading unit attachedthereto.

More specifically, as the firing rod 220 is moved in the distaldirection from its resting (e.g., initial) position, the first actuationof the position sensor 231 is activated by the first indicator 320 awhich denotes that operation of the surgical instrument 10 hascommenced. As the operation continues, the firing rod 220 is movedfurther distally to initiate clamping, which moves first indicator 320 ato interface with clamp position sensor 232. Further advancement of thefiring rod 220 moves the second indicator 320 b to interface with theposition sensor 232 which indicates that the surgical instrument 10 hasbeen fired.

As discussed above, the position calculator 416 is coupled to a lineardisplacement sensor 237 disposed adjacent to the firing rod 220. In oneembodiment, the linear displacement sensor 237 may be a magnetic sensor.The firing rod 220 may be magnetized or may include magnetic materialtherein. The magnetic sensor may be a ferromagnetic sensor or a HallEffect sensor which is configured to detect changes in a magnetic field.As the firing rod 220 is translated linearly due to the rotation of thedrive motor 200, the change in the magnetic field in response to thetranslation motion is registered by the magnetic sensor. The magneticsensor transmits data relating to the changes in the magnetic field tothe position calculator 416 which then determines the position of thefiring rod 220 as a function of the magnetic field data. In oneembodiment, a portion of the firing rod 220 may be magnetized. Forexample, the threads of the internally-threaded portion 212 or othernotches (e.g., indicators 320 a and/or 320 b) disposed on the firing rod220 may include or be made from a magnetic material. This allows forcorrelation of the cyclical variations in the magnetic field with eachdiscrete translation of the threads as the magnetized portions of thefiring rod 220 are linearly translated. The position calculator 416thereafter determines the distance and the position of the firing rod220 by summing the number of cyclical changes in the magnetic field andmultiplies the sum by a predetermined distance between the threads(e.g., the screw pitch) and/or notches.

In one embodiment, the position calculator 416 is coupled to one or moreswitches 421 which are actuated by the threads of theinternally-threaded portion 212 or the indicators 320 a and/or 320 b asthe firing rod 220 and the firing rod coupling 190 are moved in thedistal direction. The position calculator 416 counts the number ofthreads which activated the switch 421 and then multiplies the number bya predetermined distance between the threads (e.g., the screw pitch) orthe indicators 320 a and/or 320 b.

The surgical instrument 10 also includes a speed calculator 422 whichdetermines the current speed of a linearly moving firing rod 220 and/orthe torque being provided by the drive motor 200. The speed calculator422 is coupled to the motion sensor 251, which allows the speedcalculator 422 to determine the speed of the firing rod 220 based on therate of change of the displacement of the firing rod 220.

In one embodiment, the speed calculator 422 is further coupled to therotation speed detecting apparatus 424 which includes the encoder 426.The encoder 426 transmits the pulses correlating to the rotation of thedrive motor 200 which the speed calculator 422 then uses to calculatethe linear speed of the firing rod 220. In another embodiment, the speedcalculator 422 is coupled to a rotational sensor 239 which detects therotation of the drive tube 210, thus, measuring the rate of rotation ofthe drive tube 210 which allows for determination of the linear velocityof the firing rod 220.

The speed calculator 422 is also coupled to a voltage sensor 428 whichmeasures the back electromotive force (“EMF”) induced in the drive motor200. The back EMF voltage of the drive motor 200 is directlyproportional to the rotational speed of the drive motor 200 which, asdiscussed above, is used to determine the linear speed of the firing rod220.

Monitoring of the speed of the drive motor 200 can also be accomplishedby measuring the voltage across the terminals thereof under constantcurrent conditions. An increase in a load of the drive motor 200 yieldsa decrease in the voltage applied at the motor terminals, which isdirectly related to the decrease in the speed of the motor. Thus,measuring the voltage across the drive motor 200 provides fordetermining the load being placed thereon. In addition, by monitoringthe change of the voltage over time (dV/dt), the microcontroller 500 candetect a quick drop in voltage which correlates to a large change in theload or an increase in temperature of the drive motor 200 and/or thepower source 400.

In a further embodiment, the speed calculator 422 is coupled to acurrent sensor 430 (e.g., an ammeter). The current sensor 430 is inelectrical communication with a shunt resistor 432 which is coupled tothe drive motor 200. The current sensor 430 measures the current beingdrawn by the drive motor 200 by measuring the voltage drop across theresistor 432. Since the current used to power the drive motor 200 isproportional to the rotational speed of the drive motor 200 and, hence,the linear speed of the firing rod 220, the speed calculator 422determines the speed of the firing rod 220 based on the current draw ofthe drive motor 200. The current sensor 430 may also be coupled to thepower source 400 to determine the current draw thereof which allows foranalysis of the load on the end effector 160. This may be indicative ofthe tissue type being stapled since various tissue have differenttensile properties which affect the load being exerted on the surgicalinstrument 10 and the power source 400 and/or the motor 200.

The speed calculator 422 may also be coupled to a second voltage sensor(not explicitly shown) for determining the voltage within the powersource 400 thereby calculating the power draw directly from the source.In addition, the change in current over time (dl/dt) can be monitored todetect quick spikes in the measurements which correspond to a largeincrease in applied torque by the drive motor 200. Thus, the currentsensor 430 is used to determine the speed and the load of the drivemotor 200.

In addition, the velocity of the firing rod 220 as measured by the speedcalculator 422 then may be compared to the current draw of the drivemotor 200 to determine whether the drive motor 200 is operatingproperly. Namely, if the current draw is not commensurate (e.g., large)with the velocity (e.g., low) of the firing rod 220 then the motor 200is malfunctioning (e.g., locked, stalled, etc.). If a stall situation isdetected, or the current draw exceeds predetermined limits, the positioncalculator 416 then determines whether the firing rod 220 is at amechanical stop. If this is the case, then the microcontroller 500 canshut down the drive motor 200 or enters a pulse and/or pause mode (e.g.,discontinuous supply of power to the drive motor 200) to unlock thesurgical instrument 10 and retract the firing rod 220.

In one embodiment, the speed calculator 422 compares the rotation speedof the drive tube 210 as detected by the rotation sensor 239 and that ofthe drive motor 200 based on the measurements from and the rotationspeed detecting apparatus 424. This comparison allows the speedcalculator 422 to determine whether there is clutch activation problem(e.g., slippage) if there is a discrepancy between the rotation of theclutch 300 and that of the drive tube 210. If slippage is detected, theposition calculator 416 then determines whether the firing rod 220 is ata mechanical stop. If this is the case, then the microcontroller 500 canshut down the surgical instrument 10 or enter a pulse and/or pause mode(e.g., discontinuous supply of power to the drive motor 200), or retractthe firing rod 220.

In addition to linear and/or rotational displacement of the firing rod220 and other drive components, the surgical instrument 10 also includessensors adapted to detect articulation of the end effector 160. Withreference to FIG. 4, the surgical instrument 10 includes a rotationsensor 241 adapted to indicate the start position, the rotationaldirection and the angular displacement of the rotating housing assembly180 at the start of the procedure as detected by the shaft startposition sensor 231. The rotation sensor 241 operates by counting thenumber of indicators disposed on the inner surface of the rotation knob182 by which the rotation knob 182 has been rotated.

With reference to FIG. 1, the present disclosure provides a loading unitidentification system 440 which allows the surgical instrument 10 toidentify the loading unit 169 and to determine operational statusthereof. The identification system 440 provides information to thesurgical instrument 10 on staple size, cartridge length, type of theloading unit 169, status of cartridge, proper engagement, and the like.This information allows the instrument to adjust clamping forces, speedof clamping and firing and end of stroke for various length staplecartridges.

The loading unit identification system 440 may also be adapted todetermine and communicate to the surgical instrument 10 (e.g., a controlsystem 501 shown in FIG. 12) various information, including the speed,power, torque, clamping, travel length and strength limitations foroperating the particular end effector 160. The control system 501 mayalso determine the operational mode and adjust the voltage, clutchspring loading and stop points for travel of the components. Morespecifically, the identification system may include a component (e.g., amicrochip, emitter or transmitter) disposed in the end effector 160 thatcommunicates (e.g., wirelessly, via infrared signals, etc.) with thecontrol system 501, or a receiver therein. A signal may be sent viafiring rod 220, such that firing rod 220 functions as a conduit forcommunications between the control system 501 and end effector 160. Inanother embodiment, the signals can be sent through an intermediateinterface, such as a feedback controller 603 (FIGS. 14-16).

By way of example, the sensors discussed above, including the motionsensor 251, may be used to determine if the staples have been fired fromthe staple cartridge, whether they have been fully fired, whether andthe extent to which the beam has been retracted proximally through thestaple cartridge and other information regarding the operation of theloading unit. In certain embodiments of the present disclosure, theloading unit incorporates components for identifying the type of loadingunit, and/or staple cartridge loaded on the surgical instrument 10,including infra red, cellular, or radio frequency identification chips.The type of loading unit and/or staple cartridge may be received by anassociated receiver within the control system 501, or an external devicein the operating room for providing feedback, control and/or inventoryanalysis.

Information can be transmitted to the surgical instrument 10 via avariety of communication protocols (e.g., wired or wireless) between theloading unit 169 and the surgical instrument 10. The information can bestored within the loading unit 169 in a microcontroller, microprocessor,non-volatile memory, radio frequency identification tags, andidentifiers of various types such as optical, color, displacement,magnetic, electrical, binary and gray coding (e.g., conductance,resistance, capacitance, impedance).

In one embodiment, the loading unit 169 and the surgical instrument 10include corresponding wireless transceivers, an identifier 442 and aninterrogator 444, respectively (FIG. 1). The identifier 442 includesmemory or may be coupled to a microcontroller (e.g., microcontroller500) for storing various identification and status information regardingthe loading unit 169. Once the loading unit 169 is coupled to thesurgical instrument 10, the surgical instrument 10 interrogates theidentifier 442 via the interrogator 444 for an identifying code. Inresponse to the interrogatory, the identifier 442 replies with theidentifying code corresponding to the loading unit 169. Duringoperation, once identification has occurred, the identifier 442 isconfigured to provide the surgical instrument 10 with updates as to thestatus of the loading unit 169 (e.g., mechanical and/or electricalmalfunction, position, articulation, etc.).

The identifier 442 and the interrogator 444 are configured tocommunicate with each other using one or more of the followingcommunication protocols such as Bluetooth, ANT3, KNX®, ZWave®, X10®Wireless USB®, IrDA®, Nanonet®, Tiny OS®, ZigBee®, 802.11 IEEE, andother radio, infrared, UHF, VHF communications and the like. In oneembodiment, the transceiver 400 may be a radio frequency identification(RFID) tag either active or passive, depending on the interrogatorcapabilities of the transceiver 402.

FIG. 12 illustrates a control system 501 including the microcontroller500 which is coupled to the position and speed calculators 416 and 422,the loading unit identification system 440, the user interface 120, thedrive motor 200, and a data storage module 502. In addition themicrocontroller 500 may be directly coupled to the motion sensor 251 andvarious other sensors (e.g., first and second tissue sensors 177 and179, the load switch 230, shaft start position sensor 231, clampposition sensor 232, articulation sensor 235, linear displacement sensor237, rotational sensor 239, firing rod rotation sensor 241, motor andbattery operating module 412, rotation speed detecting apparatus 418,switches 421, voltage sensor 428, current sensor 430, and interrogator444).

The microcontroller 500 includes internal memory which stores one ormore software applications (e.g., firmware) for controlling theoperation and functionality of the surgical instrument 10. Themicrocontroller 500 processes input data from the user interface 120 andadjusts the operation of the surgical instrument 10 in response to theinputs. The adjustments to the surgical instrument 10 may includingpowering the surgical instrument 10 on or off, speed control by means ofvoltage regulation or voltage pulse width modulation, torque limitationby reducing duty cycle or pulsing the voltage on and off to limitaverage current delivery during a predetermined period of time.

The microcontroller 500 is coupled to the user interface 120 via a userfeedback module 504 which is configured to inform the user ofoperational parameters of the surgical instrument 10. The user feedbackmodule 504 instructs the user interface 120 to output operational dataon the screen 122. In particular, the outputs from the sensors aretransmitted to the microcontroller 500 which then sends feedback to theuser instructing the user to select a specific mode, speed or functionfor the surgical instrument 10 in response thereto.

The loading unit identification system 440 instructs the microcontroller500 which end effector is on the loading unit. In an embodiment, thecontrol system 501 is capable of storing information relating to theforce applied to firing rod 220 and/or end effector 160, such that whenthe loading unit 169 is identified the microcontroller 500 automaticallyselects the operating parameters for the surgical instrument 10. Thisallows for control of the force being applied to the firing rod 220 sothat firing rod 220 can drive the particular end effector 160 that is onthe loading unit in use at the time.

The microcontroller 500 also analyzes the calculations from the positionand speed calculators 416 and 422 and other sensors to determine theactual position, direction of motion, and/or speed of the firing rod 220and operating status of components of the surgical instrument 10. Theanalysis may include interpretation of the sensed feedback signal fromthe calculators 416 and 422 to control the movement of the firing rod220 and other components of the surgical instrument 10 in response tothe sensed signal. The microcontroller 500 is configured to limit thetravel of the firing rod 220 once the firing rod 220 has moved beyond apredetermined point as reported by the position calculator 416.Additional parameters which may be used by the microcontroller 500 tocontrol the surgical instrument 10 include motor and/or batterytemperature, number of cycles remaining and used, remaining batterylife, tissue thickness, current status of the end effector, transmissionand reception, and external device connection status.

In one embodiment, the surgical instrument 10 includes various sensorsconfigured to measure current (e.g., an ammeter), voltage (e.g., avoltmeter), proximity (e.g., optical sensors), temperature (e.g.,thermocouples and thermistors), and force (e.g., strain gauges and loadcells) to determine for loading conditions on the loading unit 169.During operation of the surgical instrument 10 it is desirable to knowthe forces being exerted by the surgical instrument 10 on the targettissue during the approximation process and during the firing process.Detection of abnormal loads (e.g., outside a predetermined load range)indicates a problem with the surgical instrument 10 and/or clampedtissue which is communicated to the user. Monitoring of load conditionsmay be performed by one or more of the following methods: monitoringspeed of the drive motor 200, monitoring torque being applied by thedrive motor 200, proximity of jaw members 162, 164, monitoringtemperature of components of the surgical instrument 10, measuring theload on the firing rod 220 via a strain sensor 185 (FIG. 4) and/or otherload bearing components of the surgical instrument 10. Speed and torquemonitoring is discussed above with respect to FIG. 6 and the speedcalculator 422.

In another embodiment, the firing rod 220 or other load-bearingcomponents include one or more strain gauges and/or load sensorsdisposed thereon. Under high strain conditions, the pressure exerted onthe surgical instrument 10 and/or the end effector 160 is translated tothe firing rod 220 causing the firing rod 220 to deflect, leading toincreased strain thereon. The strain gauges then report the stressmeasurements to the microcontroller 500. In another embodiment, aposition, strain or force sensor may be disposed on the clutch plate700.

During the approximation process, as the end effector 160 is clampedabout tissue, the sensors disposed in the surgical instrument 10 and/orthe end effector 160 indicate to the microcontroller 500 that the endeffector 160 is deployed about abnormal tissue (e.g., low or high loadconditions). Low load conditions are indicative of a small amount oftissue being grasped by the end effector 160 and high load conditionsdenote that too much tissue and/or a foreign object (e.g., tube, stapleline, clips, etc.) is being grasped. The microcontroller 500 thereafterindicates to the user via the user interface 120 that a more appropriateloading unit 169 and/or instrument 10 should be chosen.

During the firing process, the sensors can alert the user of a varietyof errors. Sensors may communicate to the microcontroller 500 that astaple cartridge or a portion of the surgical instrument 10 is faulty.In addition, the sensors can detect sudden spikes in the force exertedon the knife, which is indicative of encountering a foreign body.Monitoring of force spikes could also be used to detect the end of thefiring stroke, such as when the firing rod 220 encounters the end of thestapling cartridge and runs into a hard stop. This hard stop creates aforce spike which is relatively larger than those observed during normaloperation of the surgical instrument 10 and could be used to indicate tothe microcontroller that the firing rod 220 has reached the end ofloading unit 169. Measuring of the force spikes can be combined withpositional feedback measurements (e.g., from the motion sensor 251) asdiscussed with respect to position and speed calculators 416 and 422.This allows for use of various types of staple cartridges (e.g.,multiple lengths) with the surgical instrument 10 without modifying theend effector 160.

When force spikes are encountered, the surgical instrument 10 notifiesthe user of the condition and enters a so-called “pulse” or anelectronic clutching mode. During this mode the drive motor 200 iscontrolled to run only in short bursts to allow for the pressure betweenthe grasped tissue and the end effector 160 to equalize. The electronicclutching limits the torque exerted by the drive motor 200 and avoidssituations where high amounts of current are drawn from the power source400. This, in turn, limits damage to electronic and mechanicalcomponents due to overheating that accompanies overloading andhigh-current draw situations.

The microcontroller 500 may control the drive motor 200 through a motordriver via a pulse width modulated control signal. The motor driver isconfigured to adjust the speed of the drive motor 200 either inclockwise or counter-clockwise direction. The motor driver is alsoconfigured to switch between a plurality of operational modes whichinclude an electronic motor braking mode, a constant speed mode, anelectronic clutching mode, and a controlled current activation mode. Inelectronic braking mode, two terminal of the drive motor 200 are shortedand the generated back EMF counteracts the rotation of the drive motor200 allowing for faster stopping and greater positional precision inadjusting the linear position of the firing rod 220.

In the constant speed mode, the speed calculator 422 in conjunction withthe microcontroller 500 and/or the motor driver adjust the rotationalspeed of the drive motor 200 to ensure constant linear speed of thefiring rod 220. The electronic clutching mode involves repeatedengagement and/or disengagement of the clutch 300 from the drive motor200 in response to sensed feedback signals from the position and speedcalculators 416 and 422. In controlled current activation mode, thecurrent is either ramped up or down to limit damaging current and torquespikes when transitioning between static and dynamic mode to provide forso-called “soft start” and “soft stop.”

The data storage module 502 records the data from the sensors coupled tothe microcontroller 500. In addition, the data storage module 502 mayrecord the identifying code of the loading unit 169, the status of theend effector 100, the number of stapling cycles during the procedure,and other information relating to the status of components of thesurgical instrument 10. The data storage module 502 is also configuredto connect to an external device such as a personal computer, a PDA, asmartphone, or a storage device (e.g., a Secure Digital™ card, aCompactFlash® card, or a Memory Stick™) through a wireless or wired dataport 503. This allows the data storage module 502 to transmitperformance data to the external device for subsequent analysis and/orstorage. The data port 503 also allows for “in the field” upgrades ofthe firmware of the microcontroller 500.

Embodiments of the present disclosure may include a feedback controlsystem 601 as shown in FIGS. 13-16. The system includes a feedbackcontroller 603. The surgical instrument 10 is connected to the feedbackcontroller 603 via the data port 502 which may be either wired (e.g.,FireWire®, USB, Serial RS232, Serial RS485, USART, Ethernet, etc.) orwireless (e.g., Bluetooth®, ANT3®, KNX®, Z-Wave®, X10®, Wireless USB®,Wi-Fi®, IrDA®, nanoNET®, TinyOS®, ZigBee®, 802.11 IEEE, and other radio,infrared, UHF, VHF communications and the like).

With reference to FIG. 13, the feedback controller 603 is configured tostore the data transmitted to it by the surgical instrument 10 as wellas process and analyze the data. The feedback controller 603 is alsoconnected to other devices, such as a video display 604, a videoprocessor 605 and a computing device 606 (e.g., a personal computer, aPDA, a smartphone, a storage device, etc.). The video processor 605 isused for processing output data generated by the feedback controller 603for output on the video display 604. The computing device 606 is usedfor additional processing of the feedback data. In one embodiment, theresults of the sensor feedback analysis performed by the microcontroller600 may be stored internally for later retrieval by the computing device606.

The feedback controller 603 includes a data port 607 (FIG. 15) coupledto the microcontroller 600 which allows the feedback controller 603 tobe connected to the computing device 606. The data port 607 may providefor wired and/or wireless communication with the computing device 606providing for an interface between the computing device 606 and thefeedback controller 603 for retrieval of stored feedback data,configuration of operating parameters of the feedback controller 603 andupgrade of firmware and/or other software of the feedback controller603.

The feedback controller 603 is further illustrated in FIGS. 14-15. Thefeedback controller 603 includes a housing 610 and a plurality of inputand output ports, such as a video input 614, a video output 616, aheads-up (“HUD”) display output 618. The feedback controller 603 alsoincludes a screen 620 for displaying status information concerning thefeedback controller 603.

Components of the feedback controller 603 are shown in FIG. 16. Thefeedback controller 603 includes a microcontroller 600 and a datastorage module 602. The microcontroller 600 and the data storage module602 provide similar functionality as the microcontroller 500 and thedata storage module 502 of the surgical instrument 10. Providing thesecomponents in a stand-alone module, in the form of the feedbackcontroller 603, alleviates the need to have these components within thesurgical instrument 10.

The data storage module 602 may include one or more internal and/orexternal storage devices, such as magnetic hard drives, flash memory(e.g., Secure Digital^(R) card, Compact Flash^(R) card, orMemoryStick^(E)) The data storage module 602 is used by the feedbackcontroller 603 to store feedback data from the surgical instrument 10for later analysis of the data by the computing device 606. The feedbackdata may include information supplied by the motion sensor 251 and othersensors disposed within the surgical instrument 10.

The microcontroller 600 may supplant, complement, or supplement thecontrol circuitry of the surgical instrument 10. The microcontroller 600includes internal memory which stores one or more software applications(e.g., firmware) for controlling the operation and functionality of thesurgical instrument 10. The microcontroller 600 processes input datafrom the user interface 120 and adjusts the operation of the surgicalinstrument 10 in response to the inputs. The microcontroller 600 iscoupled to the user interface 120 via a user feedback module 504 whichis configured to inform the user of operational parameters of thesurgical instrument 10. More specifically, the surgical instrument 10 isconfigured to connect to the feedback controller 603 wirelessly orthrough a wired connection via a data port 407 (FIG. 6). In a disclosedembodiment, the microcontroller 600 is connected to the drive motor 200and is configured and arranged to monitor the battery impedance,voltage, temperature and/or current draw and to control the operation ofthe surgical instrument 10. The load or loads on battery 400,transmission, drive motor 200 and drive components of the surgicalinstrument 10 are determined to control a motor speed if the load orloads indicate a damaging limitation is reached or approached. Forexample, the energy remaining in battery 400, the number of firingsremaining, whether battery 400 must be replaced or charged, and/orapproaching the potential loading limits of the surgical instrument 10may be determined. The microcontroller 600 may also be connected to oneor more of the sensors of the surgical instrument 10 discussed above,including the motion sensor 251 (FIG. 6).

The microcontroller 600 is also configured to control the operation ofdrive motor 200 in response to the monitored information. Pulsemodulation control schemes, which may include an electronic clutch, maybe used in controlling the surgical instrument 10. For example, themicrocontroller 600 can regulate the voltage supply of the drive motor200 or supply a pulse modulated signal thereto to adjust the powerand/or torque output to limit system damage or optimize energy usage.

In one embodiment, an electric braking circuit may be used forcontrolling drive motor 200, which uses the existing back electromotiveforce of rotating drive motor 200 to counteract and substantially reducethe momentum of drive tube 210. The electric braking circuit may improvethe control of drive motor 200 and/or drive tube 210 for stoppingaccuracy and/or shift location of powered surgical instrument 10.Sensors for monitoring components of the powered surgical instrument 10to help inhibit overloading of the powered surgical instrument 10 mayinclude thermal-type sensors, such as thermal sensors, thermistors,thermopiles, thermo-couples and/or thermal infrared imaging and providefeedback to the microcontroller 600. The microcontroller 600 may controlthe components of powered surgical instrument 10 in the event thatlimits are reached or approached and such control can include cuttingoff the power from the power source 400, temporarily interrupting thepower or going into a pause mode and/or pulse modulation to limit theenergy used. The microcontroller 600 can also monitor the temperature ofcomponents to determine when operation can be resumed. The above uses ofthe microcontroller 600 may be used independently of or factored withcurrent, voltage, temperature and/or impedance measurements.

The result of the analysis and processing of the data by themicrocontroller 600 is output on video display 604 and/or the HUDdisplay 622. The video display 604 may be any type of display such as anLCD screen, a plasma screen, electroluminescent screen and the like. Inone embodiment, the video display 604 may include a touch screen and mayincorporate resistive, surface wave, capacitive, infrared, strain gauge,optical, dispersive signal or acoustic pulse recognition touch screentechnologies. The touch screen may be used to allow the user to provideinput while viewing operational feedback. The HUD display 622 may beprojected onto any surface visible to the user during surgicalprocedures, such as lenses of a pair of glasses and/or goggles, a faceshield, and the like. This allows the user to visualize vital feedbackinformation from the feedback controller 603 without loosing focus onthe procedure.

The feedback controller 603 includes an on-screen display module 624 anda HUD module 626. The modules 626 process the output of themicrocontroller 600 for display on the respective displays 604 and 622.More specifically, the OSD module 624 overlays text and/or graphicalinformation from the feedback controller 603 over other video imagesreceived from the surgical site via cameras disposed therein. Themodified video signal having overlaid text is transmitted to the videodisplay 604 allowing the user to visualize useful feedback informationfrom the surgical instrument 10 and/or feedback controller 603 whilestill observing the surgical site.

FIG. 17 is a block diagram of a feedback control system 1700 forcontrolling parameters of the motion of the firing rod 220, includingthe position and velocity of the firing rod 220, according to someembodiments. Components of the feedback control system 1700 may beimplemented in the control system 501 of FIG. 12 or the feedbackcontroller 603 of FIG. 16. The feedback control system 1700 includes themotion sensor 251, which, in some embodiments, includes a light emitterand detector unit 460, a measurement unit 470, and the microcontroller500. The light emitter and detector unit 460 may include a laser diodefor emitting light and a light sensitive transistor for detectingreflected light. In other embodiments, the light emitter and detectorunit 460 is replaced with an light emitter and detector unit that emitslight in the electromagnetic spectrum. The light emitter and detectorunit 460 focuses a light beam 461 on the surface of the firing rod 220and detects light 462 reflected from the surface of the firing rod 220.The light emitter and detector unit 460 generates a pulse signal 465with a frequency or pulse width that varies with motion of scribes orother markings 464 (see FIG. 18) transverse to the direction of motionof the surface of the firing rod 220.

The motion sensor 251 transmits the pulse signal 465 to the measurementunit 470 via a wired or wireless communications channel. For example,the motion sensor 251, in some embodiments, may be physically attachedto the firing rod 220 and the motion sensor 251 may include wirelesscommunications circuitry configured to transmit the pulse signal 465 tothe measurement unit 470 via a wireless communications link. Themeasurement unit 470 includes a counter 472 and a data processor 474.The counter 472 counts pulses in the pulse signal 465 and the dataprocessor 474 computes the frequency of the pulse signal 465 based onthe rate of the counted pulses. The count and or the computed frequencyis then used to determine the position and velocity of the firing rod220. Alternatively, in other embodiments, the measurement unit 470 mayinclude circuitry for determining the width of the pulses in the pulsesignal 465. The measured pulse width of the pulse signal 465 may then beused to determine a parameter of the motion of the firing rod 220 suchas an end or intermediate point in the stroke. For instance, the lengthand or distances between markings 464 may be varied to indicated specialconditions, such as the end point of a stroke.

The data processor 474 may determine a number of parameters of themotion of the firing rod 220 based on the count, frequency or pulsewidth of the pulse signal 465. For example, the data processor 474 (orthe position calculator 416 of FIG. 12) may determine the position atwhich a force is applied to the firing rod 220. The data processor 474may also determine the distance that the firing rod 220 moves during apredetermined time period. The data processor 474 may also determine thedirection of motion of the firing rod 220 (i.e., the data processor 474may determine whether the firing rod 220 is being inserted into theelongated shaft 140 or is being retracted out of the elongated shaft140). The data processor 474 (or the speed calculator 422 of FIG. 12)may also determine the velocity of the firing rod 220.

In one embodiment, the light emitter and detector unit 460 generates apulse signal 465 with a light frequency that varies with a change in aparameter of the light 462 reflected from the surface of the firing rod220. For example, at a first position of the firing rod 220, the lightemitter and detector unit 460 may generate a pulse signal 465 with afirst frequency when it detects light with a first wavelength reflectedfrom the bare surface 466 of the firing rod 220. At a second position,the light emitter and detector unit 460 may generate a pulse signal 465with a second light frequency when it detects light with a seconddifferent wavelength reflected from a reflective marking on the firingrod 220. The pulse signal 465 information can then be used to determinethe motion of the firing rod 220 from a first position to a secondposition. In some embodiments, the light emitter and detector unit 460may sense a change in other parameters of the light 462 reflected fromthe firing rod 220, including the intensity, polarization, or phase ofthe light 462, and generate a corresponding change in the frequency orpulse width of the pulse signal 465 from which a parameter of the motionof the firing rod 220 (e.g., the velocity of the firing rod 220) can becomputed. In other embodiments, the light emitter 460 my emit differentfrequencies of light to generate different reflected light frequenciescreated by using markings 464 having different reflected light responsesto the emitted frequencies.

FIGS. 18A and 18B are diagrams that illustrate how the pulse signal 465output from the light emitter and detector unit 460 responds to changesin a parameter of the light reflected from the surface of the firing rod220 with respect to the elongated shaft 140. In this embodiment, thelight emitter and detector unit 460 is fixed with respect to theelongated shaft 140. The firing rod 220 includes a series of markings464 that can be detected by the light emitter and detector unit 460. Insome embodiments, the markings 464 are detected by analyzing theparameters of the light reflected from the markings 464. The markings464 are separated a predetermined distance by the bare surface 466 ofthe firing rod 220. For example, the markings 464 may be spaced 1 to 5mm apart. In some embodiments, the markings 464 include a material withreflective properties that are different from the reflective propertiesof the bare surface 466 of the firing rod 220. In other embodiments, themarkings 464 may be separated by a second material that coats thesurface of the firing rod 220. The second material has reflectiveproperties that are different from the reflective properties of themarkings 464. The differences between the reflective properties of thematerials may be configured to improve or optimize the detection of themarkings 464.

As illustrated in FIG. 18A, the firing rod 220 is disposed within theelongated shaft 140 at a first position. In this first position, theemitter and detector unit 460 emits a light beam 461 on one of themultiple markings 464 on the firing rod 220 moving at a first velocityVI. The emitter and detector unit 460 then detects a parameter of thereflected light beam (e.g., the count, duration or wavelength of thelight beam) that corresponds to the reflective properties of the marking464. Upon detecting the parameter of the reflected light beam, theemitter and detector unit 460 generates a first pulse signal 467 with afirst count, a first pulse width or a first frequency. From theseparameters the position and velocity of the firing rod 220 may bedetermined.

As shown in FIG. 18B, when the firing rod 220 moves in a proximaldirection out of the elongated shaft 140 to a second position and at asecond velocity V2, the light emitter and detector unit 460 may emit alight beam on the bare surface 466 of the firing rod 220 or a material(that is different from the material of the markings 464) that coats thebare surface 466 of the firing rod 220. In this case, the emitter anddetector unit 460 generates a second pulse signal 468 with a higherpulse frequency than the first pulse signal 467 in FIG. 18A due to therelatively higher velocity. In other words, the emitter and detectorunit 460 generates the second pulse signal 468 that includes pulseshaving a narrower pulse width than the pulses in the first pulse signal467. Thus, as the firing rod 220 moves, the light emitter and detectorunit 460 detects multiple transitions from the markings 464 to the baresurface 466 of the firing rod 466 and generates shorter duration secondpulse signals 468. The counter 472 of FIG. 17 may count the second pulsesignals 468. Then, the data processor 474 of FIG. 17 may compute achange in position of the firing rod 220 based on the number oftransitions counted. For example, if the counter 472 counts three secondpulse signals 468 and assuming that the markings 464 on the firing are 1mm apart, then the data processor 474 computes a change in position of 3mm (i.e., 3 transitions×1 mm between markings 464).

In some embodiments, the measurement unit 470 computes a position and/orvelocity of the firing rod 220 based on the light reflected from thesurface of a firing rod and provides the position and/or velocityinformation to the microcontroller 500. The microcontroller 500 executesa control algorithm (e.g., a proportional control algorithm or aproportional-integral-derivative (PID) control algorithm), which usesthe computed position and/or velocity of the firing rod 220, to generatea voltage command. The voltage command is fed back 476 to apowered-drive mechanism 455 (e.g., the rotary motor 200) to form aclosed-loop feedback system. In this configuration, the position and/orvelocity of the firing rod 220 can be accurately controlled.

FIG. 19 is a flow diagram of a process 1900 for determining a parameterof the motion of a firing rod in a surgical instrument according to anembodiment. After the process 1900 starts 1901, light is emitted on thesurface of a firing rod in a surgical instrument 1902. In variousembodiments, the light may include infrared radiation, visible light orultraviolet radiation. Next, changes in a parameter of the lightreflected from the surface of the firing rod are sensed 1904. Before theprocess 1900 ends 1907, a parameter of the motion of the firing rod isdetermined based on the sensed changes 1906.

FIG. 20 is a flow diagram of a process 2000 for operating a surgicalinstrument according to another embodiment. After the process 2000starts 2001, light is emitted on the surface of a firing rod in asurgical instrument 2002. Then, changes in a parameter of the lightreflected from the surface of the firing rod are sensed 2004. Next, aparameter of the motion of the firing rod is determined based on thesensed changes in a parameter of the reflected light 2006. Then, beforethe process 2000 returns 2009 to step 2002 to emit light on the surfaceof the firing rod, the motion of the firing rod is controlled (e.g.,through a driving mechanism that physically moves the firing rod) basedon the determined parameter of the motion of the firing rod 2008.

FIG. 21 is a flow diagram of a process 2100 for determining a parameterof the motion of a firing rod in a surgical instrument according toanother embodiment. After the process 2100 starts 2101, light is emittedon the surface of a firing rod, which includes a series of markings thatchange the intensity of the reflected light 2102. Then, the intensity ofthe light reflected from the surface of the firing rod is sensed 2103. Apulse signal is generated with a frequency (or a pulse width) thatvaries with the change in intensity of the light reflected from thesurface of the firing rod 2104 and the number of transitions betweenpulse signal frequencies is counted 2106. Then, before the process 2100ends 2111, the position of the firing rod is determined based on thenumber of transitions between pulse signal frequencies 2108 (or thepulse width of pulse signals).

FIG. 22 is a flow diagram of a process 2200 for determining parametersof the motion of a firing rod in a surgical instrument according toanother embodiment. After the process 2200 starts 2201, a counter (e.g.,the counter 472 of FIG. 17) is reset 2202 at a reference position of thefiring rod (e.g., at the position where the firing rod is fullyretracted). After the counter is reset, the pulse count and duration ofa pulse signal (e.g., the pulse signal 465 generated by the lightemitter and detector unit 460) is monitored 2204. If the light emitterand detector unit detects a predetermined amount of increase in thepulse signal duration 2206 (e.g., the pulse width of the pulse signaldoubles in size) and the firing rod is moving in the distal direction2208, then the counter (e.g., the counter 472 of FIG. 17) is incrementedand the position and velocity of the firing rod are calculated 2210. Forexample, in some embodiments, the distance between markings on thefiring rod may be 1 mm. If the counter had been incremented ten times(corresponding to the detection of ten markings on the firing rod) inone second, then the position of the firing rod is 10 mm (1 cm) relativeto the reference position of the firing rod (at the time the counter wasreset) and the velocity is 0.01 m/s. In some instances, certain of themarking are placed at greater intervals to provide indications of endpoints or the direction of travel of the firing rod.

On the other hand, if the light emitter and detector unit detects apredetermined amount of increase in the pulse signal duration 2206 andthe firing rod is not moving in the distal direction 2208, but is movingin the proximal direction, then the counter is decremented and theposition and velocity of the firing rod are calculated 2212. Forexample, in some embodiments, the distance between markings on thefiring rod may be 1 mm. If the counter had been incremented ten times(corresponding to the detection often markings on the firing rod whileit was moving in the distal direction) and decremented five times(corresponding to the detection of five markings on the firing rod whileit was moving in the proximal direction), then the position of thefiring rod is 5 mm relative to the reference position of the firing rod(i.e., 10 mm in the distal direction−(minus) 5 mm in the proximaldirection=5 mm relative to the reference position).

After incrementing or decrementing the counter and calculating theposition and velocity of the firing rod 2210, 2212, the process 2200continues to monitor 2204 the pulse duration of the pulse signalgenerated by the light emitter and detector unit. It should beunderstood that the foregoing description is only illustrative of thepresent disclosure. Various alternatives and modifications can bedevised by those skilled in the art without departing from thedisclosure. Accordingly, the present disclosure is intended to embraceall such alternatives, modifications and variances. The embodimentsdescribed with reference to the attached drawing figures are presentedonly to demonstrate certain examples of the disclosure. Other elements,steps, methods and techniques that are insubstantially different fromthose described above and/or in the appended claims are also intended tobe within the scope of the disclosure.

What is claimed is:
 1. A method of determining a parameter of motion ofa firing rod in a surgical instrument, comprising: emitting light on asurface of the firing rod in the surgical instrument, wherein thesurface of the firing rod possesses varying reflective properties;sensing a change in a parameter of the light reflected from the surfaceof the firing rod; and determining a parameter of motion of the firingrod based on the sensed change in the parameter of the light reflectedfrom the surface of the firing rod.
 2. The method according to claim 1,further comprising: controlling the motion of the firing rod based onthe determined parameter of motion of the firing rod.
 3. The methodaccording to claim 2, wherein the varying reflective properties of thesurface of the firing rod are created by a plurality of markings on thesurface of the firing rod, and sensing a change in a parameter of thelight reflected from the surface of the firing rod comprises counting anumber of markings of the plurality of markings on the firing rod thatreflect the light.
 4. The method according to claim 2, wherein sensing achange in a parameter of the light reflected from the surface of thefiring rod comprises generating a pulse signal with a parameter thatvaries with the change in the parameter of the light reflected from thesurface of the firing rod, and wherein determining the parameter ofmotion of the firing rod comprises determining the parameter of motionof the firing rod based on the change in the parameter of the pulsesignal.
 5. The method according to claim 1, wherein the parameter ofmotion of the firing rod is the position of the firing rod.
 6. Themethod according to claim 1, wherein the parameter of motion of thefiring rod is the velocity of the firing rod.
 7. The method according toclaim 1, wherein the parameter of the light is phase, frequency,intensity, or polarization.
 8. A surgical instrument, comprising: ahousing; an elongated shaft extending distally from the housing anddefining a first longitudinal axis; a firing rod disposed within theelongated shaft, the firing rod having a surface with varying reflectiveproperties; a drive mechanism disposed at least partially within thehousing, the drive mechanism in mechanical cooperation with the firingrod; a light emitter that generates and emits light that is directedtowards the surface of the firing rod; and a detector that senses aparameter of light reflected from the surface of the firing rod.
 9. Thesurgical instrument according to claim 8, further comprising: ameasurement unit that determines a parameter of motion of the firing rodbased on the sensed parameter of the light reflected from the surface ofthe firing rod.
 10. The surgical instrument according to claim 9,wherein the light emitter generates a pulse signal with a parameter thatvaries with a change in the sensed parameter of the light reflected fromthe surface of the firing rod, and the measurement unit determines theparameter of motion of the firing rod based on the change in theparameter of the pulse signal.
 11. The surgical instrument according toclaim 10, wherein the parameter of the pulse signal is a frequency ofthe pulse signal.
 12. The surgical instrument according to claim 10,wherein the parameter of the pulse signal is a pulse duration of thepulse signal.
 13. The surgical instrument according to claim 9, whereinthe varying reflective properties of the surface of the firing rod arecreated by a plurality of markings on the surface of the firing rod, andwherein the measurement unit includes a counter that counts a number ofmarkings of the plurality of markings that are exposed to the lightemitted from the light emitter based on a change in the sensed parameterof the light reflected from the surface of the firing rod.
 14. Thesurgical instrument according to claim 9, wherein the parameter ofmotion of the firing rod is a position of the firing rod.
 15. Thesurgical instrument according to claim 9, wherein the parameter ofmotion of the firing rod is a velocity of the firing rod.
 16. Thesurgical instrument according to claim 9, further comprising: a controlunit that controls the drive mechanism based on the parameter of motionof the firing rod determined by the measurement unit.
 17. The surgicalinstrument according to claim 8, wherein the sensed parameter of thelight is phase, frequency, intensity, or polarization.